Glass having a low ultrasonic propagation time temperature coefficient

ABSTRACT

A glass having a low ultrasonic wave propagation time temperature coefficient, preferably for transverse waves of about 4 MHz. is disclosed having the following composition in weight percent: SiO2+B2O3 65-83 (B2O3) 0-014 3 Alkali oxides 9-20 TiO2 26TiO2+PbO 5-22As2O3 and/or Sb2O3 0.3-1.5 The glass is particularly adapted for use as a delay line, i.e., a means to retard the propagation of signal between two points.

United States Patent 2,664,359 l2/l953 Dingledy 2,727,214 12/1955 McSkimin....

Inventors App]. No. Filed Patented Assignee Priority GLASS HAVING A LOW ULTRASONIC PROPAGATION TIME TEMPERATURE COEFFICIENT 9 Claims, No Drawings U.S.Cl

Int. Cl

Field of Search 106/53, 52, 54,50; 333/29, 33, 30

References Cited UNITED STATES PATENTS 2,799,590 7/1957 Armistead 106/53 3,154,425 10/1964 l-looveretal.. 106/53 3,173,730 3/1965 Hoover 106/53X 3,475,704 10/1969 Van DerBurgt 333/30 OTHER REFERENCES Hamilton, E. H. et al., Properties of Sodium Titanian Silicate Glasses, in Journ. of Res. N. B. 8., 61, 1958, pp. 89- 94, QlN65 Primary Examiner-Helen M. McCarthy Assistant Examiner-W. R. Satterfield Attorney-Burgess, Dinklage & Sprung ABSTRACT: A glass having a low ultrasonic wave propagation time temperature coefficient, preferably for transverse waves of about 4 MHz. is disclosed having the following composition in weight percent:

SiO B 0 65*83 2 3) 0 3 Alkali oxides 9-20 TiOz 2-6 TiO PbO 5-22 AS203 and/or Sb O;, 0.3-1.5

The glass is particularly adapted for use as a delay line, Le, a means to retard the propagation of signal between two points.

GLASS HAVING A LOW ULTRASONIC PROPAGATION TIME TEMPERATURE COEFFICIENT This invention relates to a glass having a low ultrasonic wave propagation time temperature coefficient. More particularly this invention relates to a glass having a low ultrasonic propagation time temperature coefficient and intended for use in connection with transverse waves of approximately 4 MHz.

The use of delay lines to retard the propagation of a signal between two points is known. It is also known that glass can be used as a material in fabricating such delay lines. An electrical signal, whose propagation speed in copper wire is about equai to the speed of light is transformed into mechanical vibrations and propagated through a glass rod (delay line). its rate of propagation is thereby made equal to that of sound passing through a solid medium, which is of course much slower. At the other end of the glass rod, a transducer converts the mechanical vibrations (ultrasonic) back into an electrical alternating current.

Depending on the chemical composition of the glass rod used, delays of 2.7 to 4.6 microseconds per centimeter of propagation length can be obtained if transverse sound waves are produced. Delay lines have been developed for use in microwave application which provide delays of as much as several milliseconds.

Recently an important additional requirement has had to be met by delay lines intended for certain applications in color television reception and in computers. This requirement is that their propagation time must be constant over a fairly large temperature range. For example, for the receivers of color television based on the PAL system, it is required that the relative change in propagation time (l/z)(dz/fl"), be less than 2'l0'6 per degree centigrade over a temperature range of about to 60 C. This requirement is a very high one, if it is taken into consideration that the relative change in propagation time in glass and in other materials has a value on the order of l X10 per degree Centigrade.

The propagation time 1 of sound waves through a glass body having outside dimensions which are large in comparison to the wavelength is given by z=I/v,, wherein 1 is the length of the travel of the sound in the glass body and v, is the velocity of G the transverse sound waves. v,, in turn, is equal to wherein G represents the torsional modulus and p the density of the glass.

As the temperature T changes, both the length I and the sound velocity v, change, and the relative change in the propagation time 1/z)(dz/dl) is equal to Therefore it becomes minimal whenever the temperature coefficient of the transverse sound velocity [3 is equal to the coefficient of thermal expansion at. This equilibrium between the two magnitudes, however, can be obtained only over a certain temperature range.

The primary object of the invention is to provide a glass suitable for ultrasonic delay lines having a'small propagation time temperature coefficient for ultrasonic waves.

It is a further object of the present invention to provide a glass suitable for ultrasonic delay lines having a small propagation time temperature coefficient for ultrasonic waves and which other objects and features of this invention will be apparent from the following description.

In accordance with the invention it has now been found that glasses suitable for ultrasonic delay lines and having the above properties are obtained with a glass having the following composition:

Si0,+B,0, 75-85 mole-l7 65-85 wt.-% B,0, amounting to 0-4 mole-k 0-3 wt.-% Alkali oxides 8-14 mole-96 9.0- wt.-% Tit), 1.5-5.0 mole% 2.0-6.0 wt.- Ti0,+Pb0 4-8.5 mole- 5.0-22.0 wt.-% As,0, and/or Sb,0, 0.l-O.3 mole-k 0.3-1.5 wt.-%

The use of glass having the above composition results in that the propagation time characteristic passes through a minimum somewhere between 20 C. and 75 C. and that the variation in the delay time within the range between 20 below and 20 above this minimum propagation time amounts to less than 8X10.

It has furthermore been found in accordance with the invention that, in order for the minimum of the propagation time to be produced in the range of 10 C. of room temperature, it is important that the quantity of U 0 amount to from 0 to 2 wt.- the quantity of Na 0 amount to from O to l 2 wt.-%, and the K 0 quantity amount to between 0 and 20 wt.-%, and that the quotient of 2 alkali oxide in mole-percent E T10 m mole-percent be between 3.0 and 5.5.

It has furthermore been found to be particularly advantageous for the total of the TiO, and PhD present to amount to between 4 and 8.5 mole-%, the TiO, content amounting to between 1.5 and 5 mole-% and the PhD content amounting to between 0 and 6 mole-%.

1n the table which follows, examples of compositions in accordance with the invention in percent by weight are set out as illustrating glasses according to the invention.

These glasses have a minimum in their propagation time characteristic in the vicinity of room temperature, while at the same time the temperature-dependence curve is very flat. ln addition to the chemical composition the table includes information on the coefficients of expansion (or), the transformation temperature (Tg), the specific gravity (s), the temperature minimum of the propagation time (T,,) and the maximum relative variation of the propagation time Az/z between T,,20 C. and T,,+20 C.

In order to compensate for the devitrification tendency of the glass compositions according to the invention, it is advantageous to add up to 2 percent by weight of alkaline earth oxides, CdO, ZnO, A1 0 ZrO and W0 the total not to exceed 5 percent by weight. Such addition while decreasing the devitrification tendency does not have any considerable effect on the temperature stability of the propagation time. In order to achieve a high constancy in the propagation time, it is important to cool the glasses slowly, i.e., at rates of 1.0 C./hr. to 05 C./hr. because this minimizes the after effects. The advantages of the glasses in accordance with the invention over glasses having a higher lead content are the lower thermal expansion, the higher transformation temperature, and the lower specific gravity. The first two qualities are favorable for the welding on of the ceramic transducers, and the last contributes to low weight in the electronic component.

The following example is givenin order to illustrate more clearly the method of preparing a glass in accordance with the invention:

A batch mixture consisting of For a lOO-liter Oxides Wt.-% Raw Materials batch so K,CO, KNo, Tio,

smo,

209.58 kg. 44.82 kg. 54.l3 kg. 1404 kg. 1.13 kg.

TiO, Sb,0;

TABLE Compoxilians in Percent by Weigh! oxide content amounts to 8-14 moleas follows: the Li O content amounts to -4 mole-%, the Na O content amounts to O-l 2 mole-% and the K 0 content amounts to O-l 4 mole-%.

6. A glass according to claim 1 having the following com- 7. A glass according to claim 1 having the Oxides l 2 3 4 5 6 7 $102 74.7 82.5 80.2 76.9 66.3 66.4 68.4 B203 2.0 20 L1 0 Na O .5 7. K20 .6 Z. ZnO 1.0 PhD .4 15.2 18.5 M203 1.0 T102 3.0 2.7 ZrO; l.l AS205 0.3 0.3 S13 0,

a- (-30-+70C) 77.3 56.8 58.6 59.5 65.2 6L3 71.2

Tg C 573 538 475 508 514 529 490 To "C 65 55 40 75 42 I8 30 between TF2) c 1.5 10- l.6-l0- 6.2-10 6.2-10 4.7-10- 3.9-10- (1.240

We claim: position: 1. A glass having an ultrasonic wave propagation time-temperature coefficient (z)(dz/dt) minimum at a temperature (I in the range of about 20 to 75 C., and a variation dz/z in said coefficient in the temperature range of T -20 C. to T,,+20 C. L 6 of less than 8X10", consisting essentially of: 2

Mole-3E Wt.-% position.

sio,+B,0, 75-s5 65-83 Siox B,O, amounting to 0-4 0-3 B203 Alkali metal oxides 8-14 9-20 N320 T10, 1.5-5.0 2-6 K10 T1o,+1 bo 4-8.5 5-22 pbo As,0, and/or sb,o, 0.1-0.3 0.3-1.5 02 Pbo 0-6 0-1s.5 A820a wherein the ratio alkali metal oxide molepercent TiO: mole-percent is from 3.0-5.5.

2. A glass according to claim 1, containing as additional ingredients up to 2 percent by weight of the alkaline earth oxides, CdO, ZnO, A1 0 ZrO, and W0 the total of said additional ingredients not exceeding 5 wt.%.

3. A glass according to claim 1, the thermal expansion coefficient for 30 to +70 C. times 10 being 56.8-77.3; the transformation temperature being 475-573 C.; and the specific gravity being 2.38-2.79.

4. A glass according to claim 2, the thermal expansion coefficient for 30 to +70 C times 10 being 56.8-77.3; the transformation temperature being 475-573 C.; and the specific gravity being 2.38-2.79.

5. A glass according to claim 1, wherein said alkali metal 8. A glass according to claim 1, having th position:

SiO: 8,0; Na O K,O ZnO Pbo Al,0;, TiO, ZrO, Sb,0,

9. A glass according to claim position:

SiO Na,0 TiO Sb,0

following comfollowing com- 1 having the following comgig UNITED STATES PATENT oFFicE CERTIFICATE OF CORREiITIQN Patent No. 3,615,770 Da ted Oct. 26, 1911' Inventofls) Marga Faulstich et a1.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 1, line 37, ohafige "1 x 10 Col. 3, line 31, change "(z) (dz/fit)" to and on' the same line change "(1 to a e. (1 N Signed and sealed this 25th day of April 1972.

Attest:

EDWARD MELAETCHER; JR ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents 601.1, line 71, (3rd col.) ehange "65-85 wt.-'Z" 

2. A glass according to claim 1, containing as additional ingredients up to 2 percent by weight of the alkaline earth oxides, CdO, ZnO, Al2O3, ZrO, and WO3, the total of said additional ingredients not exceeding 5 wt.%.
 3. A glass according to claim 1, the thermal expansion coefficient for -30* to +70* C. times 107 being 56.8- 77.3; the transformation temperature being 475* - 573* C.; and the specific gravity being 2.38- 2.79.
 4. A glass according to claim 2, the thermal expansion coefficient for -30* to +70* C times 107 being 56.8- 77.3; the transformation temperature being 475* - 573* C.; and the specific gravity being 2.38- 2.79.
 5. A glass according to claim 1 wherein said alkali metal oxide content amounts to 8-14 mole-%, as follows: the Li2O content amounts to 0- 4 mole-%, the Na2O content amounts to 0- 12 mole-% and the K2O content amounts to 0- 14 mole-%.
 6. A glass according to claim 1 having the following composition: SiO281.9 mole-% 74.7 wt.-% K2O 13.9 mole-% 19.9 wt.-% TiO2 4.1 mole-% 5.0 wt.-% Sb2O3 0.1 mole-% 0.4 wt-%.
 7. A glass according to claim 1 having the following composition: SiO278.9 mole-% 66.3 wt.-% B2O3 2.0 mole-% 2.0 wt.-% Na2O 8.6 mole-% 7.5 wt.-% K2O 2.0 mole-% 2.6 wt.-%Pbo 5.9 mole-% 18.4 wt.-% TiO2 2.4 mole-% 2.7 wt.-% As2O3 0.2 mole-% 0.5 wt.-%.
 8. A glass according to claim 1 having the following composition: SiO277.9 mole-% 66.4 wt.-% B2O3 2.0 mole-% 2.0 wt.-% Na2O3 8.5 mole-% 7.5 wt.-% K2O 1.9 mole-% 2.5 wt.-% ZnO 0.9 mole-% 1.0 wt.-% Pbo 4.8 mole-% 15.2 wt.-% Al2O3 0.7 mole-% 1.0 wt.-% TiO2 2.6 wt.-% 3.0 wt.-% ZrO2 0.6 mole-% 1.1 wt.-% Sb2O3 0.1 mole-% 0.3 wt.-%
 9. A glass according to claim 1 having the following composition: SiO282.5 wt.-% Na2O 12.0 wt.-% TiO2 5.0 wt.-% Sb2O3 0.5 wt.-%. 